The goals of this study are to: (1) estimate the individual differences in personality and well-being change in older adults over time, (2) estimate exposure and determinants of day-to-day events and stressors among older adults, as well as relating these estimates to the longer-term, multi-year trajectories, and (3) examine differences among persons in intraindividual change due to health, life events, and sociodemographic characteristics. The study population is from the VA Normative Aging Study (NAS), a 35-year old study of aging (age range: 49-90 years). Two investigations will be conducted including a new longitudinal data collection over three waves, and combining these data with existing longitudinal data collected from 1975 to 1999. A cohort of women are added, specifically the wives of the NAS men. In the second study, a daily diary design is employed within a subset of NAS husband-wife pairs over an 8-day period. Together, the two studies investigate change and stability in personality and well-being over different periods of time. The fact that most theories on well-being and personality focus on change or stability at the personal level coupled with research at the sample level, only modeling intraindividual change will reconcile this discrepancy. The multi-year study will allow the examination of change and stability in personality traits and well-being, whereas the 8-day diary study permits the examination of state variability in stressors and affective components of well-being. Individual growth modeling to estimate intraindividual trajectories and hierarchical modeling to evaluate the impact of immediate stressors and day-to-day affect will be employed respectively. Gender and personality influences on daily variation will also be examined. Husband-wife personality interrelationship will be examined. Day-to-day variability (e.g., affect) will be examined as potential predictors of multi-year personality and well-being trajectories. With this study a better understanding of why some people change and why some do not will be achieved.